The present invention relates to a method for transmission of data frames in a mobile network as defined in the non-characteristic part of claim 1, and a data embedding arrangement to carry out this method as defined in the noncharacteristic part of claim 2.
A method, and implicitly also an arrangement, for transfer of mobile voice and data frames in ATM (Asynchronous Transfer Mode) format is already known in the art, e.g. from the article xe2x80x98Wireless ATMxe2x80x94Tales of a Marriagexe2x80x99 from the author Jan Kruys. This article was published in the magazine xe2x80x98Telecommunicationsxe2x80x99 in February 1997. Therein, a rapid growth of the use of ATM technology in mobile networks is predicted because of ATM""s adequateness for high-quality multimedia applications in comparison with alternative technologies. If ATM technology is used in the conventional way for transmission of data frames between a first and second element of a mobile network, for instance between a base transceiver station and a transcoding and rate adaptation unit of a GSM (Global System for Mobile Communications) network, each ATM cell contains an amount of data frames. Indeed, in the conventional way either a single mobile data frame is empacked in an ATM cell or several mobile data frames are empacked in AAL2 (ATM Adaptation Layer) minicells which are combined into ATM cells. The minicells which are combined in one ATM cell may come from different users/channels. In such a system, if mobile data packets from different channels are to be transferred nearly simultaneously from the first to the second mobile network element, a very high peak cell rate is required to be able to respect delay requirements for all these channels. The basic reason for this technical problem is related to the synchronisation on the radio interface where all data coming from all channels is received nearly at the same time (within the same TDMA frame), and in order to avoid different delays for different users a quite high peak cell rate is required when conventional transport mechanisms are used.
An object of the present invention is to provide a method and arrangement of the above known type, but which enable to respect delay requirements for different channels without the need for additional network resources (additional bandwidth to obtain high peak cell rates).
According to the invention, this object is achieved by the method defined in claim 1 and the data embedding arrangement defined in claim 2.
Indeed, not all information of a mobile data frame has to be available at the receiving mobile network element to start decoding the data frame. Each data frame therefor can be split up at least in a first subframe containing data which have to be available in the second mobile network element to start decoding the data frame, and a second subframe containing data which may arrive later at the transcoder in the second mobile network element to continue decoding the data frame. The first subframes of different channels are embedded in minicells which are combined into ATM cells so that the transcoders of the different channels can already start decoding the data frames of several channels upon receipt of a single ATM cell. In this way, network resources are used more optimally since delay requirements of several channels can be respected without provision for additional bandwidth.
It is to be noticed that the term xe2x80x98comprisingxe2x80x99, used in the claims, should not be interpreted as being limitative to the means listed thereafter. Thus, the scope of the expression xe2x80x98a device comprising means A and Bxe2x80x99 should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.
Similarly, it is to be noticed that the term xe2x80x98coupledxe2x80x99, also used in the claims, should not be interpreted as being limitative to direct connections only. Thus, the scope of the expression xe2x80x98a device A coupled to a device Bxe2x80x99 should not be limited to devices or systems wherein an output of device A is directly connected to an input of device B. It means that there exists a path between an output of A and an input of B which may be a path including other devices or means.
An advantageous implementation of the present invention is defined by claim 3.
In this way, by adaptively ordering minicells of different channels depending for example on the activity of these different channels, an increased performance is obtained without provision for additional network resources.
Another additional advantageous feature of the data embedding arrangement according to the present invention is defined by claim 4.
The use of minicells with different lengths provide an even more increased performance because the lengths of the minicells, if well-selected, are suitably adapted to the subframes to be embedded therein.
A data embedding arrangement as defined in claims 2, 3 or 4 may form part of a base transceiver station or a transcoding and rate adaptation unit of a GSM (Global System for Mobile Communications) network, as is indicated by claims 5 and 6 respectively. The transcoding and rate adaptation unit may be integrated as a server within the base station controller or mobile switching center as indicated by claims 7 and 8 respectively. The mobile switching center will only be influenced if the transcoding and rate adaptation unit functionality is moved to after the mobile switching center (this is not the case in GSM but might be the case in UMTS) or in case of transcoder free operation which will be introduced in GSM and UMTS (Universal Mobile Telecommunication System).